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Application characteristics of various protein expression and purification tags

Update time : 2020-11-13

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Application characteristics of various protein expression and purification tags
Protein tag refers to the protein or polypeptide expressed by fusion with the target protein during the preparation of recombinant protein. The functions of the tag protein are generally: to promote the solubility and stability of the target protein; to facilitate the detection of the target protein; and to facilitate target protein purification and expression.

Small molecular weight protein tag

This type of tag is generally a polypeptide sequence, and its main function is to facilitate protein purification and can also be used for protein detection and identification. 

Due to its small molecular weight, it basically does not affect the structure of the target protein, and is generally expressed as a fusion with a protein with a larger molecular weight. 

Small molecule tags usually include: 6*His tag, Flag tag, c-Myc tag, HA tag, Arg6 tag, AviTag, etc. The most commonly used tags are 6*His tag, Flag tag and c-Myc tag.


HIS tag
Main application: His tag fusion protein is also used for protein-protein and protein-DNA interaction research.
Features:
  1. The molecular weight of the label is small;
  2. It can be purified in the presence/denaturing conditions of non-ionic surfactants. The former is used in the purification of highly hydrophobic proteins, and the latter is particularly useful in the purification of inclusion body proteins;
  3. It can be applied to a variety of expression systems, with mild purification conditions;
  4. It can be used with other affinity tags to construct parental affinity tags;
  5. The immunogenicity is relatively low.

Flag tag
Main applications: Widely used in protein expression, purification, identification, functional research and protein interactions and other related fields, with higher expression efficiency in eukaryotic expression systems.
Features:
  1. It usually does not interact with the target protein, which is convenient for researchers to conduct downstream research on the fusion protein.
  2. The target protein can be directly subjected to affinity chromatography by FLAG. This chromatography is non-denaturing purification, which can purify the active fusion protein with high purification efficiency.
  3. It can be recognized by anti-FLAG antibodies, so the FLAG-containing fusion protein can be detected and identified by Western Blot, ELISA and other methods.
  4. FLAG fused to the N-terminus can be excised by enterokinase (DDDK) to obtain a specific target protein.

Since the small molecular weight tag does not affect the structure of the protein, it generally does not need to be removed, which can realize large-scale production. 

There are corresponding small molecular weight tag antibodies on the market, which can facilitate the detection of protein expression. Therefore, small molecular weight tags are used in experiments and production. Used most.


Large molecular weight label

The main function of the large molecular weight tag protein is to promote the solubility of the target protein, promote the correct folding of the protein, and improve the stability, and the large molecular weight tag can increase the expression of the protein. 

The macromolecular tag protein is usually linked to the target protein by restriction sites, which is convenient for excision after expression and purification. 

Due to the large molecular weight of the tag, the spatial structure may affect the target protein, and it can also be used between the tag protein and the target protein. 

Add link peptides between. Common macromolecular tags are: GST tag, Sumo tag, TrxA tag, MBP tag, etc.


GST tag
Main application: GST fusion expression system is widely used in the expression of various fusion proteins, and can be expressed in host cells such as E. coli and yeast.
Features:
  1. It is a highly soluble protein;
  2. It can be expressed in large quantities in E. coli, which can increase the expression level.
  3. In most cases, the fusion protein is soluble in aqueous solution and forms dimers.

GST tags can be easily detected by enzymatic analysis or immunoassay. Tags help protect recombinant proteins from degradation by extracellular proteases and improve their stability. 

In most cases, the GST fusion protein is completely or partially soluble.


Sumo tag
SUMO tag protein is a small ubiquitin-like modifier, and one of the important members of the ubiquitin polypeptide chain superfamily. It can be used as a protein tag or as a site for enzyme cleavage and hydrolysis .
Features:
  1. Increase the expression of fusion protein
  2. Resistant to protease hydrolysis, thereby promoting the correct folding of the target protein
  3. Improve the water solubility of the destination sheet
  4. It can be completely excised by SUMO proteolytic enzyme to obtain target protein without label

Protein tags play a very important role in the production of recombinant proteins, enabling the expression and purification of various proteins to be realized. 

In the selection of tags during the experiment, tags can be selected according to the purpose of the experiment. 

The protein expression service of generalbiosystems can be based on customer experiments. Purpose, customize a suitable protein expression plan, and quickly express the target protein through suitable tags.